The present invention relates to a diesel fuel preheater for engines, especially motor vehicle engines, in which the diesel fuel is heated electrically and by a heat exchanger.
Electrically heated diesel fuel preheaters as well as preheaters for engines in which the cooling water, the motor oil, the exhaust gases, the engine block itself and similar heat sources are used to preheat the diesel fuel are known.
However, it is disadvantageous that electric diesel fuel preheating requires a relatively great and long lasting current consumption with a respective load on the battery and the electric on-board system. When heat exchangers are used, it is disadvantageous that the heating effect is usually very slow. This might be compensated for by oversizing the respective heat exchanger, however, this results in return in an overheating of the diesel fuel which may lead to the formation of vapor bubbles within the fuel.
Originally, the primary function of such diesel fuel preheaters has been to prevent the partial solidification of the diesel fuel at low temperatures in order to improve the flow characteristics especially through the fuel filter to thereby prevent cold start and running problems of the engine. Nowadays, a diesel fuel preheater should also fulfill other requirements with respect to environmental issues by reducing the cold running characteristics, improving the engine performance and reducing the fuel consumption as well as the emission values.
In view of these requirements a fast and steeply inclined fuel heating to a certain temperature of approximately 50.degree. to 60.degree. C. is desirable and the temperature should be maintained at this level in order to quickly provide favorable defined conditions for the engine performance. Known diesel fuel preheaters do not fulfill the above mentioned requirements or they have the disadvantage of being of a complicated design and expensive, requiring a lot of space and providing low adaptability. A good adaptability is desirable in order to provide a universal application of only a few sizes of diesel fuel preheaters for various engines.
It is therefore an object of the present invention to provide fast and favorable fuel heating in a simple, economic, and reliable manner with a space and cost conserving preheater and to prevent thereby the known disadvantages.